Defrost of refrigeration systems is controlled regularly during normal mode of operation. However, during first start-up of the refrigeration system and during re-start of the refrigeration system, defrost as controlled during normal mode of operation may lead to false cooling operation or lack of cooling operation of items or locations to be cooled by the refrigeration system. Therefore, during first start-up and during re-start after loss of electrical power, special modes of operation must be used for obtaining cooling and for obtaining correct cooling. Often, special modes of operation are controlled manually, or special modes of operation have to be monitored carefully by a person for ensuring subsequent cooling at all and for ensuring subsequent correct cooling.